Compressor unloading system



Jan. 28, 1964 BEEMAN 3,119,551

COMPRESSOR UNLOADING SYSTEM Filed Jan. 2, 1962 FIG. I

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ATTORNEYS United States Patent 3,119,551 Patented Jan. 28, 1964 Office 3,119,551 CGMERESSOR UNLQADING SYSTEM Lyle Beeman, 1050 Eeaconsfield, Gresse Pointe Park, Mich.

Filed Jan. 2, 1962, Ser. No. 163,613 7 Claims. (Cl. 2311-31) This invention relates to air compressor systems and particularly to an air compressor control system for venting the compression chambers of an air compressor and preventing an undue load on the air compressor When the operation of the air compressor is initiated.

In my copending application, Serial No. 102,423, titled Air Compressor Control Mechanism, filed April 12, 1961, there is disclosed and claimed a single control system which will start and stop the compressor, unload the compressor air in the cylinder of the compressor when the compressor is stopped, and stop the operation of the compressor in case of overload.

It is an object of this invention to provide an improved air compressor system wherein the unloading of the compressed air in the compression chambers or cylinders is continued for a predetermined length of time after the compressor is started, permitting the compressor to attain operating speed without undue load on the compressor motorl It is a further object of the invention to provide such a system which is simple and low in cost.

Basically, the invention comprises a system including a pressure responsive control valve mechanism responsive to the pressure in the air tank or reservoir to control the starting and stopping of the compressor and utilizing a diaphragm valve between the pressure responsive valve and the compression charnber of the air compressor. One side of the diaphragm valve communicates with the reservoir through the pressure responsive valve so that com- Inunication to one side of the diaphragm is opened by the pressure responsive valve when the air compressor is stopped and closed when the air compressor is started. The other side of the diaphragm valve communicates With the compression chambers or cylinders of the air compressor. The diaphragm controls a spring loaded exhaust valve to the atmosphere which is opened when the air compressor is stopped and closed when the air compressor is started after a predetermined period of time as presently described. The one side of the diaphragm valve which communicates with the reservoir is provided with a vent opening to the atmosphere. When the air compressor is started, a predetermined quantity of air is entrapped be tween the pressure responsive valve and one side of the diaphragm and slowly escapes through the vent opening. This maintains the exhaust valve open for a sufiicient time, permitting the air compressor to achieve operating speed. After substantially all the entrapped air has passed through the vent opening, the diaphragm moves, permitting the spring loaded valve to close the exhaust from the compression chamber of the air compressor to the atmosphere. In this fashion, the load is not applied on the air compressor until after the air compressor motor has achieved substantial operating speed.

In the drawings:

FIG. 1 is a side elevation of an air compressor system embodying the invention.

FIG. 2 is a part sectional, partly diagrammatic view on an enlarged scale of a portion of the apparatus shovvn in FIG. 1.

Referring to the drawings, air compressor 10 having or more compression chambers or cylinders -11 is adapted to be operated by an electric motor 12 through an endless belt 13 trained over pulleys 14, 15. The compression chamber 11 is connected through a line 16 and one-way check valve 17 to an air reservoir 18. When the compressor is operating, air passes through the check valve 17 to the reservoir 18. When the compressor is stopped, the check valve 17 closes communication to the chamber 11.

The operation of the motor 12 is controlled by a pressure responsive valve or control mechanism 19 that can be of the type described in my copending application. Serial No. 102,423, titled Air Compressor Control Mechanism, filed April 12, 1961, and includes a diaphragm 20 that communicates through a line 21 to the reservoir 18. When the pressure in the reservoir passes below a predetermined point, the pressure control mechanism 19 initiates the operation of the motor 12 to cause air compressor 10 to supply air under pressure to the reservoir 18. When the pressure reaches the desired point, control mechanism 19 operates to deenergize the motor 12.

As further shown in FIGS. 1 and 2, a diaphragm valve 22 is interposed between the control mechanism 19 and compression chamber 11. Specifically, the diaphragm valve 22 includes a body 23 having a passage 24 that is connected to the line 16. A diaphragm 25 is mounted on the end of the body 23 and a cap 26 fastened around the periphery of the diaphragm to hold the diaphragm in position and define a chamber 27. The chamber 27 communicates through a nipple 28 and line 29 with a fitting 31) on control mechanism 19. The fitting 30 includes a passage 31 communicating through a line 32 to the conduit 21 extending between control mechanism 19 and air reservoir 18.

As further shown in FIG. 2, a ball 33 is yieldingly urged against a seat 34 in passage 25 by a spring 35. In addition, valve body 23 includes an exhaust opening 36 to the atmosphere which communicates with passage 24. The ball 33 is adapted to be moved away from its seat *34 by a rod 37 fixed to a plate 38 and slidable in an opening 37a in valve body 23. Plate 38 is positioned adjacent the diaphragm 25 and is moved against the ball 33 when the diaphragm is moved to the left, as presently described. A needle valve 39 controls the escape of air from chamber 27 through a small exhaust or vent opening 40 in the cap 26.

The pressure responsive valve or control mechanism 19 {includes an arm 41 that is adapted to be moved into and out of position to seat a ball 42 on a seat 43 in the passage 31. When the compressor is in operation, the arm 41 forces the ball 42 against the seat 43. When the compressor is stopped, the 41 moves away from the ball 42, permitting the ball 42 to be moved upwardly by air and permitting air from the reservoir 18 to move the diaphragm 25 to the left, as shown in FIG. 2. This forces the ball 33 away from the seat 34 and, in turn, permits air to escape from the compression chamber 11 of the compressor to the atmosphere through passage 24 and exhaust opening 36. By this action, the compression chamber 11 or cylinder of the compressor is unloaded, permitting the compressor to start easily when it is again operated.

According to the invention, when the pressure responsive valve 19 energizes the motor 12 to again operate the compressor, the 41 moves the ball 42 against the seat 43 closing off communication between one side of the diaphragm 25 and the reservoir 18 and entrappinrg a quantity of air in the chamber 27 and line 29. This maintains the diaphragm toward the left, holding rod 37 in position to maintain the ball 33 away from the seat 34 so that the compression chamber 11 continues to be exhausted to the atmosphere. The air entrapped in the chamber 27 and line 29 escapes slowly through the vent opening 40 to the atmosphere. This maintains the ball 33 away from seat 34 open for a predetermined length of time permitting the compressor to attain speed without any load on the compression chamber 11. As the air escapes from the chamber 27 and line 29, the diaphragm 27 returns to the position shown in PEG. 2, permitting the ball 33 to move against the seat 34 under the action of the spring 35, closing the exhaust to the atmosphere.

It can thus be seen that there has been provided a means for simply and economically maintaining the exhaust of the compression chambers to the atmosphere when the compressor is initially operated so that the compressor can achieve speed without undue load. Especially in larger compressor-s, this permits a more ethcient operation of the compressor with a resultant saving in size of the prime mover required to initiate operation of the compressor.

I claim:

1. In a compressor system, the combination comprising an air compressor having at least one chamber which is periodically changed in size to compress air, a reservoir to which the air is supplied by the compressor when it is operated, a control mechanism communicating with and responsive to the pressure in the reservoir for controlling the operation of the compressor, and valve means interposed between and communicating with the control mechanism and the compression chamber of the compressor, said valve means having a vent opening and means the-rein operable to open said vent opening when said pressure responsive control mechanism operates to stop said compressor, a shut-oil valve communicating with said valve means and said reservoir and being operable by said pressure responsive control mechanism to entrap a predetermined quantity of air from the reservoir between the valve means and the pressure responsive control mechanism when the pressure responsive control mechanism operates to start the compressor, said valve means including means therein permitting said entrapped air to escape at a predetermined rate and means being operable upon escape of said entrapped air to close the vent opening to said compression chamber.

2. In a compressor system, the combination comprising an air compressor having at least one compression chamber, a reservoir to which air is supplied from said compression chamber, a pres-sure responsive valve communicating with and responsive to the pressure of in said reservoir for controlling the operation of said compressor, and valve means including a diaphragm interposed between and communicating with said pressure responsive valve and said compression chamber, one side of said diaphragm communicating with said compression chamber and communicating with an exhaust passage to the atmosphere, the other side of said diaphragm communicating with said reservoir, a shut-off valve operable by said pressure responsive valve to open and close communication between said other side of said diaphragm and said reservoir, said valve means having a vent opening communicating with said other side of said diaphragm and a valve operable by said diaphragm for controlling said exhaust passage such that when the pressure responsive valve interrupts the operation of the compressor, the pressure of air in the reservoir forces the diaphragm to move and open the exhaust opening and when the pressure responsive valve starts the compressor the shut-off valve is operated to close the communication from the other side of the diaphragm to the air reservoir thereby entrapping a predetermined quantity of air under pressure so that the predetermined quantity escapes through the vent opening, and the diaphragm is thereafter permitted to move so that the valve closes the exhaust opening and loads the compression chamber of the compressor.

3. The combination set forth in claim 2 including means for varying the size of the vent opening.

4. In a compressor system, the combination comprising a compressor having at least one compression chamber, a reservoir, a line extending from said compression chamher to said reservoir, a check valve in said line, a pressure responsive valve communicating with said reservoir, a

diaphragm valve including a diaphragm interposed between and communicating with the pressure responsive valve and the compression chamber, a shut-oif valve operable by said pressure responsive valve to shut off communication to one side of the diaphragm in said diaphragm valve when the compressor is operated and to open communication to said one side of the diaphragm when the compressor is stopped, said diaphragm valve having an exhaust passage 'from the other side of said diaphragm to the atmosphere and a valve communicating with the one side of said diaphragm and controlled by said diaphragm and operable to open said exhaust passage when the communication from said air reservoir to the said one side of the diaphragm is opened upon stoppage of the compressor thereby connecting the exhaust passage to the compression chamber, said diaphna'gm valve including a vent opening adjacent said one side of the compression chamber whereby when the pressure responsive valve starts the compressor and closes the shut-cit valve so that communication between said one side of said diaphragm and the air reservoir is interrupted, a quantity of air is entnapped between said one side of said reservoir and said pressure responsive valve thereby maintaining said exhaust valve open until the entrapped air has escaped through said vent opening permitting the exhaust valve to close and shut off communication between said exhaust passage and said compression chamber.

5. In a compressor system, the combination comprising a compressor having at least one compression chamber, a reservoir, a line extending from said compression chamber to said reservoir, a check valve in said line, a pressure responsive valve communicating with said reservoir, a diaphragm valve interposed between and comrnunicating with the pressure responsive valve and the compression chamber, said diaphragm valve including a valve body having a diaphragm therein, a shut-01f valve operable by said pressure responsive valve to shut oil communication to one side of the diaphragm in said dia phragm valve when the compressor is operated and open communication to said one side of the diaphragm valve when the compressor is stopped, said diaphragm valve body having an exhaust passage to the atmosphere on the opposite side of said diaphragm and a valve in said valve body controlled by said diaphragm and adapted to open said exhaust passage when the communication from said air reservoir to the said one side of the diaphragm is opened upon stoppage of the compressor thereby connecting the exhaust passage to the compression chamber, said diaphragm valve including a vent opening adjacent said one side of the compression chamber whereby when the pressure responsive valve starts the compressor and closes the shut-off valve so that communication to the air reservoir is interrupted, a quantity of air is entrapped between said one side of said reservoir and said pressure responsive valve thereby maintaining said exhaust valve open until the entrapped air has escaped through said vent opening permitting the exhaust valve to close and shut off communication between said exhaust passage and said compression chamber.

6. The combination set forth in claim 5 wherein said shut-off valve comprises a fitting, a ball, said fitting having a seat against which said ball is adapted to move to close the shut-off valve, said pressure responsive valve having an arm adapted to be moved by actuation of said pressure responsive valve to hold said ball against said seat.

7. The method of controlling the operation of an air compressor having at least one compression chamber which comprises utilizing the pressure in an air reservoir to which compressor supplies air for controlling the operation of the compressor, and for venting said compression chamber to the atmosphere when the compressor is interrupted, entrapping a predetermined guantity of air from the reservoir in response to initiation of compressor operation and utilizing said predetermined quantity of air to maintain communication open between the compression chamber and the atmosphere when the compressor operation is initiated, and venting said entrapped air at a predetermined rate so that after a predetermined unit of time, the communication to the atmosphere is closed.

1,117,394 Joleen Nov. 17, 1914 6 Tatum Sept. 9, Black Aug. 7, Bartholomew Nov. 1, Evelyn Feb. 27, Bartholomew Nov. 19, McIntyre Jan. 20, Yeomans May 5, Lamhcrton Nov. 29, Yerger May 28, 

1. IN A COMPRESSOR SYSTEM, THE COMBINATION COMPRISING AN AIR COMPRESSOR HAVING AT LEAST ONE CHAMBER WHICH IS PERIODICALLY CHANGED IN SIZE TO COMPRESS AIR, A RESERVOIR TO WHICH THE AIR IS SUPPLIED BY THE COMPRESSOR WHEN IT IS OPERATED, A CONTROL MECHANISM COMMUNICATING WITH AND RESPONSIVE TO THE PRESSURE IN THE RESERVOIR FOR CONTROLLING THE OPERATION OF THE COMPRESSOR, AND VALVE MEANS INTERPOSED BETWEEN AND COMMUNICATING WITH THE CONTROL MECHANISM AND THE COMPRESSION CHAMBER OF THE COMPRESSOR, SAID VALVE MEANS HAVING A VENT OPENING AND MEANS THEREIN OPERABLE TO OPEN SAID VENT OPENING WHEN SAID PRESSURE RESPONSIVE CONTROL MECHANISM OPERATES TO STOP SAID COMPRESSOR, A SHUT-OFF VALVE COMMUNICATING WITH SAID VALVE MEANS AND SAID RESERVOIR AND BEING OPERABLE BY SAID PRESSURE RESPONSIVE CONTROL MECHANISM TO ENTRAP A PREDETERMINED QUANTITY OF AIR FROM THE RESERVOIR BETWEEN THE VALVE MEANS AND THE PRESSURE RESPONSIVE CONTROL MECHANISM WHEN THE PRESSURE RESPONSIVE CONTROL MECHANISM OPERATES TO START THE COMPRESSOR, SAID VALVE MEANS INCLUDING MEANS THEREIN PERMITTING SAID ENTRAPPED AIR TO ESCAPE AT A PREDETERMINED RATE AND MEANS BEING OPERABLE UPON ESCAPE OF SAID ENTRAPPED AIR TO CLOSE THE VENT OPENING TO SAID COMPRESSION CHAMBER. 